Solar control coated glass

ABSTRACT

A solar-control glass that has acceptable visible light transmission, absorbs near infrared wavelength light (NIR) and reflects midrange infrared light (low emissivity mid IR) along with a preselected color within the visible light spectrum for reflected light is provided. Also provided is a method of producing the improved, coated, solar-controlled glass. The improved glass has a solar energy (NIR) absorbing layer comprising tin oxide having a dopant such as antimony and a low emissivity control layer (low emissivity) capable of reflecting midrange infrared light and comprising tin oxide having fluorine and/or phosphorus dopant. A separate iridescence color suppressing layer as described in the prior art is generally not needed to achieve a neutral (colorless) appearance for the coated glass, however an iridescence suppressing layer or other layers may be combined with the two layer assemblage provided by the present invention. If desired, multiple solar control and/or multiple low emissivity layers can be utilized. The NIR layer and the low emissivity layer can be separate portions of a single tin oxide film since both layers are composed of doped tin oxide. A method of producing the coated solar control glass is also provided.

This application is a divisional of U.S. patent application Ser. No.09/699,681, filed Oct. 30, 2000, of David A. Russo, Clem S. McKown,Christophe Roger, and Jeffrey L. Strickler for “Solar Control CoatedGlass”.

REFERENCE TO RELATED APPLICATION

The present application which is a continuation-in-part of U.S. patentapplication Ser. No. 09/249,761 filed Feb. 16, 1999 now U.S. Pat. No.6,218,018 which is incorporated herein by reference.

BACKGROUND OF INVENTION

This invention relates to coated glass used in residential,architectural and vehicle windows and miscellaneous applications whereboth solar control and low emissivity properties are desired. Thecoatings for solar control and low emissivity contain tin oxide havingvarious dopants. The invention avoids the need for an anti-iridescenceunderlayer. The glass articles may be of any shape but are typicallyflat or curved. The glass composition can very widely but is typicallysoda lime glass produced by the float process. It may be annealed, heatstrengthened or tempered.

DESCRIPTION OF PRIOR ART

Solar-control is a term describing the property of regulating the amountof solar heat energy which is allowed to pass through a glass articleinto an enclosed space such as a building or an automobile interior. Lowemissivity is a term describing the property of an article's surfacewherein the absorption and emission of mid-range infrared radiation issuppressed, making the surface a mid-range infrared reflector andthereby reducing heat flux through the article by attenuating theradiative component of heat transfer to and from the low emissivitysurface (sometimes referred to as Low E). By suppressing solar heatgain, building and automobile interiors are kept cooler, allowing areduction in air conditioning requirements and costs. Efficient lowemissivity coatings improve comfort during both summer and winter byincreasing the thermal insulating performance of a window.

Important to commercially acceptable coated glass articles which possessboth solar-control and low emissivity properties are, of course,economic processes for producing the articles and durability andmaintenance of associated properties such as light transmission,visibility, color, clarity and reflection.

As explained below, various technologies have been employed to meet therequirement for solar-control and low emissivity glass, however, no onesystem has successfully met all of the performance requirements in aneconomic manner.

Many coatings and coating systems cause iridescent colors to develop inthe coated article. This may be caused by the chemical composition ofthe coating, the thickness of an individual layer or layers, or aninteraction of the substrate and coatings to incident light. Suchiridescence can, in some cases, be minimized or eliminated by placing ananti-iridescence layer between the glass substrate and the firstcoating. The use of an interference layer between the glass and asubsequent functional layer or layers to suppress iridescence or colorreflection was first demonstrated by Roy G. Gordon, and was the subjectof U.S. Pat. No. 4,187,336, issued Feb. 5, 1980. The Gordon technologyhas been the state of the art for coated solar control glass asevidenced by recently issued U.S. Pat. No. 5,780,149 (McCurdy et al,Jul. 14, 1998) which applied two layers to obtain solar control on topof a Gordon type interference layer. The interference layer frequentlycontains silicon dioxide. Surprisingly, the present invention representsa dramatic breakthrough and eliminates the need for a Gordon typeunderlayer to control reflected color.

U.S. Pat. No. 3,149,989 discloses compositions of coatings useful inproducing radiation reflecting (solar-control) glass. At least twocoatings are used with the first coating, adhered to the glasssubstrate, being comprised of tin oxide doped with a relatively highlevel of antimony. The second coating is also comprised of tin oxide andis doped with a relatively low level of antimony. The two films may besuperimposed, one on another, or may be applied to opposite sides of theglass substrate. In either case, these solar-control coatings do notcontribute significant low emissivity properties to the glass article.

U.S. Pat. No. 4,287,009 teaches a heat absorbing glass designed toconvert incident sun rays into heat energy that is transferred to aworking fluid for heat transfer. Accordingly, the coated glass absorbsat least 85% of the solar wavelength range rays and has a relatively lowemissivity characteristic of less than 0.2. The coatings are positionedon the outside of the glass (i.e. the side facing the sun) and the fluidfor heat transfer contacts the inside surface of the glass. The coatingscomprise a first coating of metal oxides deposited on the smooth glasslayer which oxides are selected from tin, antimony, indium, and iron anda second coating of metal oxides deposited on the first coating selectedfrom the same group of metals. The films as designed will have very lowvisible transmissions and no teaching on the control of reflected coloris given.

U.S. Pat. No. 4,601,917 teaches liquid coating compositions forproducing high-quality, high-performance, fluorine-doped tin oxidecoatings by chemical vapor deposition. One of the uses of such coatingsis in the production of energy-efficient windows, also known in thetrade as low-E or low-E windows. Methods of producing the coated glassare also described. This patent does not teach how to produce coatedglass articles which possess both solar-control and low emissivityproperties.

U.S. Pat. No. 4,504,109, assigned to Kabushiki Kaisha Toyota Chou,describes glass coated with infrared shielding multilayers comprising avisible light transparent substrate and an overlying componentlamination consisting of “at least one infrared shield layer and atleast one interferential reflection layer alternatively lying on eachother . . . ” Indium oxide doped with Sn is used in the examples as theinfrared shield layer and TiO₂ was used as the interferential shieldlayer. In order to reduce iridescence the infrared shield layer and theinterferential reflection layer thickness must have a value of onequarter lambda (lambda/4) with a permissible deviation of from 75% to130% of lambda/4. Although other formulations are disclosed for theinfrared shield layer and the interferential reflection layer such asSnO₂ with or without dopants, (see column 6 lines 12 to 27), however,the specific combination of doped SnO₂ layers of the present inventionthat accomplishes solar control, low emissivity and anti-iridescencewithout requiring a lambda/4 thickness limitation is neither disclosednor exemplified to suppress iridescence or color reflection.

U.S. Pat. No. 4,583,815, also assigned to Kabushiki Kaisha Toyota Choudescribes a heat wave shield laminate consisting of two indium tin oxideoverlayers containing different amounts of tin. Antireflection layers,above or below the indium tin oxide layers are also described. Otherformulations are disclosed for the infrared shield layer and theinterferential reflection layer such as SnO₂ with a dopant that becomesa positive ion with a valence of +5 such as Sb, P, As, Nb, Ta, W, or Moor an element such as F which readily becomes a negative ion with avalence of −1, (see column 22 lines 17 to 23). However, the specificcombination of doped SnO₂ layers of the present invention thataccomplishes solar shielding, low emissivity and anti-iridescence isneither disclosed nor exemplified. There is no claim to tin oxide layersnor any teaching in the specification to describe the composition ofsuch layers, e.g. the ratio of dopant to tin oxide. It should also benoted that the teaching leads to the use of the same dopant in bothlayers (indium tin oxide) whereas in the instant patent application, onelayer must contain a different dopant than the other layer.

U.S. Pat. No. 4,828,880, assigned to Pilkington PLC, describes barrierlayers which act to inhibit migration of alkali metal ions from a glasssurface and/or act as color suppressing underlayers for overlyinginfrared reflecting or electrically conducting layers. Some of thesecolor suppressing layers are used in solar-control or low emissivityglass construction.

U.S. Pat. No. 4,900,634 assigned to Glaverbel discloses a pyrolyticcoating of tin oxide containing a mixture of fluorine and antimonydopants coated on glass and imparting low emissivity and a specific hazereduction factor of at most 1.5.

U.S. Pat. No. 5,168,003, assigned to Ford Motor Company, describes aglazing article bearing a substantially transparent coating comprisingan optically functional layer (which may be low emissivity or solarcontrol) and a thinner anti-iridescence layer which is a multiplegradient step zone layer. Antimony doped tin oxide is mentioned as apossible alternative or optional component of the exemplified lowemissivity layer.

U.S. Pat. No. 5,780,149, assigned to Libbey-Owens-Ford describes solarcontrol coated glass wherein at least three coating layers are present,first and second transparent coatings and an iridescence suppressinglayer lying between the glass substrate and the transparent upperlayers. The invention relies upon the transparent layers having adifference in refractive indices in the near infrared region greaterthan the difference of indices in the visible region. This differencecauses solar heat to be reflected in the near IR region as opposed tobeing absorbed. Doped metal oxides which have low emissivity properties,such as fluorine doped tin oxide, are used as the first transparentlayer. Metal oxides such as undoped tin oxide are used as the secondlayer. No NIR absorbing combinations are described.

EP 0-546-302-B1 issued Jul. 16, 1997 and is assigned to Asahi Glass Co.This patent describes coating systems for solar-control, heat treated(tempered or bent) glass comprising a protection layer based on a metalnitride. The protection layer or layers are used to overcoat thesolar-control layer (to prevent it from oxidizing during thermaltreatment). As a solar control layer, many examples are providedincluding tin oxide doped with antimony or fluorine. However, thespecific combination of doped SnO₂ layers of the present invention thataccomplishes solar control, low emissivity and anti-iridescence withoutfollowing Gordon's teachings is neither disclosed nor exemplified.

EP 0-735-009-A1 is a patent application that was published in February1996 and is assigned to Central Glass Co. This patent applicationdescribes a heat-reflecting glass pane having a multilayer coatingcomprising a glass plate and two layers. The first layer is a highrefractive index metal oxide based on Cr, Mn, Fe, Co, Ni or Cu, thesecond layer is a lower refractive index film based on a metal oxidesuch as tin oxide. Doped layers and low emissivity or NIR absorbingcombinations are not disclosed.

WO 98/11031 This patent application was published in March 1998 andassigned to Pilkington PLC. It describes a high performancesolar-control glass comprising a glass substrate with coatingscomprising a heat-absorbing layer and a low emissivity layer of a metaloxide. The heat-absorbing layer may be a metal oxide layer. This layermay be doped tungsten, cobalt, chromium, iron molybdenum, niobium orvanadium oxide or mixtures thereof. The low emissivity layer may bedoped tin oxide. In a preferred aspect of the invention, aniridescence-suppressing layer or layers is incorporated under thecoating comprising a heat-absorbing layer and a low emissivity layer.This application does not disclose or suggest the specific combinationof doped SnO₂ layers of the present invention that accomplishes solarcontrol, low emissivity and anti-iridescence without requiring a“Gordon” type underlayer to suppress iridescence or color reflection.

Canadian Patent 2,193,158 discloses an antimony doped tin oxide layer onglass with a tin to antimony molar ratio o 1:0.2 to 1:0.5 that reducesthe light transmission of the glass.

Dopant Effects in Sprayed Tin Oxide Films, by E. Shanthi, A. Banerjeeand K. L. Chopra, Thin Solid Films, Vol 88, 1981 pages 93 to 100discusses the effects of antimony, fluorine, and antimony-fluorinedopants on the electrical properties of tin oxide films. The articledoes not disclose any optical properties of the antimony-fluorine filmsnor the effect on transmitted or reflected color.

UK Patent Application GB 2,302,101 A assigned to Glaverbel describes aglass article coated with an antimony/tin oxide film of at least 400 nmcontaining an Sb/Sn molar ratio from 0.05 to 0.5, with a visibletransmittance of less than 35%. The films are applied by aqueous sprayCVD and are intended for privacy glass applications. Haze reducingundercoats are taught as well as thick layers with low Sb/Sn ratioswhich have low emissivity properties as well as high solar absorbency.It also teaches that it is possible to provide one or more additionalcoating layers to achieve certain desirable optical properties. None ofthese properties other than haze are mentioned. The application teachesnothing about thinner layers, the use of more than one dopant, or thecontrol of film color.

UK Patent Application GB 2,302,102 A also assigned to Glaverbeldescribes a glass substrate coated with a Sn/Sb oxide layer containingtin and antimony in a molar ratio of from 0.01 to 0.5, said layer havingbeen deposited by CVD, whereby the coated substrate has a solarfactor(solar heat gain coefficient) of less than 0.7. The coatings areintended for window applications and have luminous transmittancesbetween 40 and 65% and thicknesses ranging from 100 to 500 nm. Hazereducing undercoats are claimed and low emissivity can be imparted tothe coatings by a judicious choice of the Sb/Sn ratio. Like the previousapplication, the teaching of providing one or more additional coatinglayers to achieve certain desirable optical properties is mentioned.Also low emissivity layers of fluorine doped tin oxide can be depositedover the Sb/Sn layers or fluorine components can be added to the Sb/Snreactants to give low emissivity films which contain F, Sb and Sn. Thelast two methods were not favored because of the added time and cost ofadding a third layer and the fact that the emissivity of the Sb/F filmswas raised and not lowered. No mention of color control or colorneutrality is found.

GB 2,200139, assigned to Glaverbel teaches a method of depositing acoating by the spray application of solutions containing tin precursors,fluorine containing compounds and it least one other dopant selectedfrom the group antimony, arsenic, vanadium, cobalt, zinc, cadmium,tungsten, tellurium or manganese.

Previously, glass manufacturers have managed heat transport throughwindows by the use of absorbing and/or reflecting coatings, glass tints,and post-applied films. Most of these coatings and films are designed tocontrol only one portion of the solar heat spectrum, either the NIR,i.e. near infrared component of the electromagnetic spectrum having awavelength in the range of 750-2500 nm or the mid IR component of theelectromagnetic spectrum having a wavelength on the range of 2.5-25microns. A product has been designed to control the entire heatspectrum, however Sputtered metal/dielectric film stacks whileeffective, have limited durability and must be protected and sealedwithin the center section of a multipane insulated glass unit (IGU).What is needed is a total solar control film or combination of filmsthat can be easily applied by pyrolytic deposition during the glassmaking operation which yields an article which has an acceptable visibletransmission, reflects or absorbs the NIR, reflects the mid-IR, and isneutral or close to neutral in color.

The above references either alone or in combination do not teach orsuggest the specific combination of doped SnO₂ layers of the presentinvention that accomplishes solar control, low emissivity andanti-iridescence without requiring a “Gordon” type underlayer.

SUMMARY OF THE INVENTION

The present invention provides an improved solar-control glass that hasacceptable visible light transmission, absorbs near infrared wavelengthlight (NIR) and reflects midrange infrared light (low emissivity or LowE) along with a preselected color within the visible spectrum forreflected light that can be controlled to a specific color or be madeessentially colorless (“neutral” as defined hereinafter). Also providedis a method of producing the improved, coated, solar-control glass. Theimproved glass coating is a tin oxide coating with various dopants andhaze modifiers in specific layers of the coating. One layer is a solarenergy (NIR) absorbing layer comprising tin oxide having a dopant suchas antimony. Another layer in the tin oxide coating is a low emissivitycontrol layer capable of reflecting midrange infrared light andcomprising tin oxide having fluorine and/or phosphorus dopant. Aseparate iridescence color suppressing layer as described in the priorart such as a “Gordon” layer is generally not needed to achieve aneutral (colorless) appearance for light reflected off the coated glass,however an iridescence suppressing layer or other layers may be combinedwith the multilayer tin oxide coating provided by the present invention.If desired, multiple solar control and/or multiple low emissivity layerscan be utilized. The NIR layer and the low emissivity layer are separateportions of a single tin oxide film since both layers are composed ofdoped tin oxide. A method of producing the coated solar control glass isalso provided. In addition, the present invention controls or changesthe color of transmitted light through the addition of color additivesto the NIR layer. Surprisingly the dopant fluorine that produces anoncolored tin oxide film functions as a color additive when added as anadditional dopant to the NIR layer and modifies the color of transmittedlight through the NIR film. Also provided are haze reducing dopants inspecific layers of the tin oxide coating.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 through 4 and 8 through 15 depict a cross-section of coatedglass having different numbers of layers or films in different stackingsequences for the tin oxide layer on a glass substrate. FIGS. 5 and 6graphically depict the solar control achieved with antimony doped filmsat various concentrations of dopant and various film thicknesses onwindow panes, i.e. a single pane of glass, or on insulated glass units(IGU) which are a composite of at least two glass panes. FIG. 7 depictsthe color spectrum in terms of Commission Internationale de L'Exclairage(C.I.E.) x and y coordinates and the specific color achievable withvarious film thickness and dopant concentrations. The Englishtranslation for C.I.E. is International Commission on Illumination FIG.15 shows haze reduction values for tin oxide coatings of the presentinvention with and without haze reducing additives in the NIR layer, 28.FIGS. 16, 17, 18 and 19 graphically depict data developed in theexamples.

OBJECTS OF THE INVENTION

An object of the invention is to prepare a transparent article withcontrolled reflected color even neutral color as defined herein,) thatwill absorb solar near infrared (NIR) wavelength radiation and reflectmid-range infrared heat (low emissivity) comprising glass having a tinoxide coating composed of two thin film layers containing doped SnO₂with haze reducing additives or dopants in at least one of the layers.Another object is the application of the layers by atmospheric pressurechemical vapor deposition (CVD) techniques, or by other processes suchas solution spray or vaporized/sublimed liquids/solids can be utilized.The preferred method of application for this invention is atmosphericpressure CVD using vaporized liquid precursors. Another object is toprovide multiple solar control and/or low emissivity layers along withother layers in combination with the solar control or low emissivitylayer. Another object is to provide a solar control film or combinationof films that can be easily applied by pyrolytic deposition during theglass making operation which yields an article which has an acceptablevisible transmission, reflects or absorbs the NIR, reflects the mid-IR(low-E), and is neutral or close to neutral in color, the production ofwhich is an object of the present invention. Another object of theinvention is to control the color of transmitted light independentlyfrom the color of reflected light by the addition of color additives inthe NIR layer.

DETAILED DESCRIPTION OF INVENTION AND PREFERRED EMBODIMENTS

Solar control and low emissivity coated glass is produced by depositingon a heated transparent substrate at least two layers, a low emissivitylayer comprising a SnO₂ film containing fluorine and/or phosphorusdopant and a NIR absorbing layer comprising a SnO₂ film containing as adopant antimony, tungsten, vanadium, iron, chromium, molybdenum,niobium, cobalt, nickel or mixtures thereof. This combination has beenfound to effectively control the solar and radiative heat portions ofthe electromagnetic spectrum such that a window coated with these filmswill have greatly enhanced properties.

Solar control properties are typically expressed in terms of solar heatgain coefficient (SHGC) and U-value. SHGC is a measure of the totalsolar heat gain through a window system relative to the incident solarradiation, while the U-value (U) is the total heat transfer coefficientfor the window. The SHGC of the coated glass is primarily dependent onthe thickness and the antimony content of the NIR absorbing film (seeFIGS. 5 and 6) while the U-value depends primarily on the film'semissivity and the window construction. SHGC measured at center of glasscan range from about 0.40 to 0.80 while U values measured at center ofglass can vary from about 0.7-1.2 form a single pane coated with thepreferred embodiment films. In an insulated glass unit (IGU) the SHGC'sdecrease to ˜0.30 with U-values as low as ˜0.28.

Both the reflected and transmitted color of the coated glass of thepresent invention can be controlled. In addition the amount of visiblelight transmitted through the coated glass can be controlled betweenabout 25-80% by controlling the thickness of the NIR and low emissivityfilms and the concentration of dopant in the NIR film. Transmittedcolor, i.e. the color of light transmitted through the coated glass canbe controlled separately from the reflected color by the addition of acolor-effective quantity of a color additive to the NIR layer of thecoating. The reflected color can vary from almost neutral to red,yellow, blue or green and can be controlled by varying the filmthickness and dopant content of the layers. Surprisingly, colorneutrality as defined herein can be achieved for reflected color withoutthe need of an anti-iridescent layer. Although the refractive indices ofthe NIR and low emissivity films are different, the reflected color doesnot depend on classical interference phenomena originally discovered byGordon (U.S. Pat. No. 4,187,336). Observed reflected color isunexpectedly controlled by the combination of absorption and reflectionachieved by the NIR layer (absorption) and the reflection achieved bythe low-emissivity layer or layers. The absorption of the NIR layer canbe controlled by varying the thickness of its SnO₂ layer and theconcentration of the dopant in the NIR layer, usually antimony. Thereflectance of the low emissivity layer can be controlled by varying thethickness of its SnO₂ layer and the concentration of the dopant in thelow emissivity layer, usually fluorine. The low emissivity layercomposed of SnO₂ containing a fluorine or phosphorus dopant is sometimesabbreviated herein as TOF or TOP while the NIR layer of SnO₂ when itcontains an antimony dopant is sometimes abbreviated herein as TOSb.

The preferred embodiment of this invention utilizes a tin oxide coatingthat has a fluorine doped tin oxide (TOF) layer as the low emissivitylayer with an antimony doped tin oxide (TOSb) layer as the NIR layer andwith a haze reducing additive in at least one of the layers preferablein the layer deposited directly onto the glass. TOF films and theirdeposition processes onto glass are known in the art and referred to aslow emissivity films. The NIR absorbing film is also a SnO₂ film butcontains a different dopant than the low emissivity layer. The dopant inthe NIR layer is preferably antimony although the dopant can be anelement selected from the group consisting of antimony, tungstenvanadium, iron, chromium, molybdenum, niobium, cobalt, nickel, andmixtures thereof. A mixture of one or more dopants can be used in theNIR layer, however the low emissivity layer must contain a lowemissivity dopant that imparts significant conductivity to the layersuch as fluorine or phosphorus, although other dopants may be used incombination with the low emissivity dopant. Since the low emissivity andthe NIR layers of the present invention both utilize SnO₂ as the metaloxide matrix containing a dopant, the NIR and the low emissivity layersare preferably part of a single film having a dopant gradient or layershaving different dopants. A single film utilizing a dopant gradient isdepicted in FIG. 3 as film 16. In film 16 there is a dopant gradientwith the NIR dopant having a higher concentration than the otherdopant(s) at one surface of the film, either surface 18 or 22, and thelow emissivity dopant having a higher concentration than the otherdopants at the other surface of the film. This results in a change orgradient in the concentrations of the NIR and low emissivity dopantsbetween surface 18 and surface 22. At some intermediate point 20 betweensurface 18 and surface 22 the concentration of the NIR dopant changesfrom being the highest concentration dopant on one side of point 22 tono longer being the highest concentration dopant on the other side ofpoint 22. FIG. 8 shows the low e film, 10, above the NIR film 12, TheNIR film 12 in FIG. 8 has a concentration gradient for the NIR dopant inthe tin oxide film with a lower concentration of the dopant closer tothe low e film 10. The coated glass of FIG. 9 is similar to thestructure shown in FIG. 8 with the exception that the concentrationgradient of the NIR dopant, usually antimony, is higher near the low efilm 10 and lower nearer the substrate. Film 12 is different then film16 shown in FIG. 3 in that film 12 is a NIR film while film 16 has bothNIR and low e properties and contains both a low e dopant and a NIRdopant with a concentration gradient for the low e dopant and aconcentration gradient for the NIR dopant. FIGS. 10, 11, 12 and 13 showthe NIR layer as two distinct films, 28 and 30. Film 28 is shown asbeing thicker than film 30 and the total thickness of the NIR layer isthe sum of the thicknesses of films 28 and 30 and should be within therange of thicknesses stated above for the NIR layer and preferably from80 to 300 nm. In FIGS. 10 and 11, films 28 and 30 are adjacent eachother, while in FIGS. 12 and 13, films 28 and 30 are on opposite sidesof low e film 10. The concentration of dopant in film 28 is preferablydifferent than the concentration of dopant in film 30.

FIG. 14 shows a bilayer tin oxide film deposited directly on a glasssubstrate 14 with the lower layer 32 being one section, 34 having a hazereducing additive and other portion, 36 without an haze reducingadditive, while the top layer, 10 is a low emissivity layer such asfluorine doped tin oxide.

FIG. 15 shows haze reduction values for tin oxide coatings of thepresent invention with and without haze reducing additives in the NIRlayer, 32. Shown are four glass substrates each having an antimony dopedtin oxide NIR layer, 32, about 2400 angstroms thick beneath a fluorinedoped low e layer, 10 each about 3000 angstroms thick. In the coatedglass on the left, haze was 1.13% verses 0.72% when TFA was added to theNIR layer shown on the second from the left. Continuing to the right inFIG. 15, the haze of the bilayer coating 32 and 10, is 0.84 when waterwas withheld during, the deposition of the first 550 (approximately)angstroms of the NIR layer, verses a haze of 0.70 shown in the far rightbilayer coated glass in which the TFA but no water was present among theprecursors that deposited the first 550 angstroms of NIR layer 32.

The preferred embodiment of this invention uses an antimony doped filmas the NIR film. Such a film can be deposited by a number of techniquesincluding spray pyrolysis PVD and CVD methods. Spray pyrolysis is knownand disclosed in patents such as Canadian patent 2,193,158. CVD methodsfor depositing SnO₂ films with or without dopants and the chemicalprecursors for forming SnO₂ films containing dopants are well known anddisclosed in U.S. Pat. Nos. 4,601,917, and 4,265,974. Preferred is CVDdeposition of the SnO₂ layers containing dopants according to knownmethods directly on a float glass manufacturing line outside of orwithin the float glass chamber utilizing conventional on-line depositiontechniques and chemical precursors as taught by U.S. Pat. No. 4,853,257(Henery). However the SnO₂ films containing dopants can be applied aslayers on glass utilizing other processes such as solution spray orvaporized/sublimed liquids/solids at atmospheric pressure. When theapplication is by solution spray the same SnO₂ precursors and dopantsare dissolved in a suitable non-reactive solvent and applied by knownspray techniques to the hot glass ribbon at atmospheric pressure.Suitable solvents for the solution spray application as taught inCanadian Patent Application 2,193,158 include alcohols such as ethanoland isopropanol, ketones such as acetone and 2-butanone, and esters suchas ethyl acetate and butyl acetate. The preferred method of applicationfor this invention is atmospheric pressure CVD using vaporized liquidprecursors. The process is very amenable to existing commercial on-linedeposition systems. The precursors of the preferred embodiments areeconomical to apply, will enable long coating times, will reduce thefrequency of system clean-out, and should be able to be used with littleor no modification to existing glass float line coating equipment,

The coatings function by a combination of reflection and absorption. Thelow emissivity film reflects mid-IR heat in the 2.5-25 micron region ofthe spectrum while the NIR absorbing film absorbs heat primarily in the750-2500 mn region. While not to be bound thereby, the theory upon whichwe account for this effect is that in the NIR region, the plasmawavelength (PL—the wavelength where the low emissivity film changes froma transmitter to a reflector of light energy) for the low emissivityfilm falls in the NIR region. In the area around the PL, the NIRabsorption is the highest for the low emissivity film and when combinedwith a NIR absorbing film, increased absorbency takes place. The NIRabsorbing films of our preferred embodiments are also dopedsemi-conductors and hence have reflective properties in the mid IR. Thisreflection coupled with the low emissivity film reflection gives anoverall higher heat reflectance in the mid IR.

Preferably the SnO₂ is pyrolyticly deposited on the glass using a tinprecursor, especially an organotin precursor compound such asmonobutyltin trichloride (MBTC), dimethyltin dichloride, dibutyltindiacetate, methyl tin trichloride or any of the known precursors for CVDdeposition of SnO₂ such as those disclosed in U.S. Pat. No. 4,601,917incorporated herein by reference. Often such organotin compounds used asprecursors for pyrolytic deposition of SnO₂ contain stabilizers such asethanol. Preferably the concentration of stabilizers is less than 1% inorder to reduce fire risks when contacting hot glass with such chemicalsin the presence of oxygen. Precursors for the dopant in the NIR layer(antimony, tungsten, vanadium, iron, chromium, molybdenum, niobium,cobalt and nickel) are preferably halides such as antimony trichloride,however alkoxides, esters, acetylacetonates and carbonyls can be used aswell. Other suitable precursors for the dopant and SnO₂ are well knownto those skilled in the art. Suitable precursors and quantities for thefluorine dopant in the low emissivity SnO₂ layer are disclosed in U.S.Pat. No. 4,601,917 and include trifluoroacetic acid,ethyltrifluoroacetate, ammonium fluoride, and hydrofluoric acid.Concentration of low emissivity dopant is usually less then 30% withpreferred concentrations of low emissivity dopant from 1% to 15% byweight of dopant precursor based upon the combined weight of dopantprecursor and tin precursor. This generally correlates to a dopantconcentration in the low e film of from 1% to 5% percent based upon theweight of tin oxide in the low e film.

In our preferred embodiments, the properties depend on the thickness ofthe low emissivity and absorbing layers as well as the antimony contentof the absorbing (NER) film. The low emissivity film thickness can rangefrom 200-450 nm with to 320 nm being most preferred. The preferred NIRabsorbing films can be deposited in a similar fashion as the lowemissivity films using such methods as disclosed in U.S. Pat. No.4,601,917. The organotin precursors for the SnO₂ can be vaporized in airor other suitable carrier gases containing a source of O₂ and inprecursor concentrations from 0.25-4.0 mol % (0.5-3.0 mol % morepreferred). SnO₂ precursor concentrations are expressed herein as apercentage based upon the moles of precursor and the moles of carriergas. Preferred concentrations of NIR dopant precursor are from about 1%to about 20% (2.5% to 7.5% more preferred and 3.0% to 6.0% mostpreferred) and are calculated using the weight of dopant precursor andthe weight of SnO₂ precursor. Particularly preferred is an antimonydopant using antimony trichloride as the precursor at about 2% to about8% by weight with about 4.0% by weight particularly preferred. Thiscorrelates to a similar antimony mass percent in the tin oxide NIR film.

The coated glass of the present invention is depicted in the figures.FIG. 1 shows the films in cross section. The film thicknesses can rangefrom 200 to 450 nm for the low emissivity film (item 10) and for the NIRfilm (item 12) from 80 to 300 nm. The preferred thickness is 250 to 350nm for the low emissivity film and 200 to 280 nm for the NIR film. Mostpreferred is 280 to 320 nm for the low e film and 220-260 nm for NIRfilm. Using films of the preferred embodiments, solar control coatedglass can be produced with a Neutral-blue Color which is defined hereinas coated glass having reflected light predominately within C.I.E.chromaticity coordinates values of x between 0.285 and 0.310 and ybetween 0.295 and 0.325. The definition of Neutral-blue is shown in FIG.7 by the area within the box labeled Neutral-blue Color. As shown inFIG. 7, with examples 15, 20 and 22, controlled or preselected reflectedcolor close to neutral color but slightly to the yellow side of neutralcan be produced (x values of up to 0.325 and y values of up to 0.33),but such essentially neutral to slightly yellow shades of reflectedcolor are not appealing to consumers. FIG. 2 shows the two films orlayers in the opposite sequence than that shown in FIG. 1. In FIG. 2,the low emissivity film is closer to the glass 14 than the NIR film 12.FIG. 3 shows the NIR and the low emissivity layers integrated into asingle SnO₂ film 16 having a dopant gradient within film 16. Film 16 hasa preponderance of one dopant (e.g. the low emissivity dopant, fluorine)at the upper surface, 18, away from the glass 14 and a preponderance ofthe other dopant (e.g. the NIR dopant such as antimony) at the filmsurface 22 nearer the glass. The concentration of dopant changes fromsurface 18 to surface 22, so that one dopant changes from greater than50% of the dopants at surface 18 to approximately 0% at surface 22. Atan intermediate point 20, below upper surface 18, the predominant dopantat that point in the film changes from the predominant dopant at surface18 to the predominant dopant at surface 22. Either the NIR dopant or thelow emissivity dopant (fluorine) can be the predominant dopant atsurface 18 with the other dopant the predominant dopant at surface 22.FIG. 4 depicts a coated glass having additional layers 24 and 26 inaddition to a low emissivity layer 10 and NIR layer 12. The additionallayers 24 and 26 can be additional low emissivity and/or NIR layers orother conventional layers used to coat glass such as a tinting layer.For example 12 can be a NIR layer (e.g. antimony doped tin), 10 a lowemissivity layer (fluorine doped tin) and 24 another NIR layer, 26 canbe another low emissivity layer or some other conventional layer. Theconcentration of dopant when more than one low emissivity layer isutilized may be the same or different and the thickness of each lowemissivity layers may also be the same or different. Likewise, when morethan one NIR layer is utilized, the concentration of dopant and theselection of dopant (antimony, tungsten, vanadium, iron, chromium,molybdenum, niobium, cobalt and nickel) can be the same or different andtie thickness of each NIR layer can be the same or different. Generallythe dopant for the NIR layer has been discussed herein mostly in termsof antimony, it must be understood that the dopant in the NIR layer canbe selected from the group consisting of antimony, tungsten, vanadium,iron, chromium, molybdenum, niobium, cobalt, nickel and mixturesthereof. Likewise, in the gradient layer embodiment of the invention asdepicted in FIG. 3, the predominant dopant at the NIR surface eithersurface 18 or 22 can be selected from the group consisting of antimony,tungsten, vanadium, iron, chromium, molybdenum, niobium, cobalt, nickeland mixtures thereof, it only being essential that the low e dopant,e.g. fluorine, be the predominant dopant at the opposite surface.Combined with a gradient layer can be one or more NIR or low emissivitylayers such as layers 10 and 12 in FIGS. 1 to 3 and/or otherconventional layers.

Water is preferably used to accelerate the deposition of SnO₂ film ontoglass as taught by U.S. Pat. No. 4,590,096 (Lindner) and used inconcentrations from ˜0.75 to 12.0 mol % H₂O based upon the gascomposition.

Another embodiment of this invention is the reduction of film haze. Hazeis due to the scattering of incident light when it strikes a surface. Itcan be caused by surface roughness due to large crystallite size, a widerange of crystallite sizes and/or particulates imbedded in the filmsurface. It can also be caused by voids (holes) in the film due to thevolatilization of an intermediate by-product such as NaCl. The filmsdeposited by this invention have haze that is predominantly caused bysurface roughness. Haze is reduced by the judicious inclusion orexclusion of certain additives in the coating process either at theglass-film interface or at the bi-layer film interface. By controllingthe rugosity within the film layers in this manner, the rugosity andhence the haze of the top layer in the bilayer tin oxide coating isreduced. This is an improvement over the prior art which obtains hazereduction by adding an auxiliary layer on top of the functional layer.The sole purpose of the prior art auxiliary layer is to level the roughsurface of the functional layer by filling in the areas betweencrystallite peaks and valleys.

One of these rugosity reducing additives is fluorine in either aninorganic form like HF or an organic form like trifluoroacetic acid(TFA) or ethyl trifluoroacetate for example. Other fluorine sourcessuitable for haze reduction are difluoroacetic acid, monofluoroaceticacid, antimony tri and pantafluoride, and ethyl trifluoroacetoacetate.When fluorine is present in all or part of the TOSb undercoat, thecrystallite size is significantly decreased and the overall film haze isreduced. SEM micrographs show that the crystallite size of the topcoathas been affected by the reduced crystallite size of the undercoat.Other additives that have been found to be effective in reducing hazeare acids such as acetic, formic, propionic, methanesulfonic, butyricand its isomers, nitric and nitrous acid. Haze also can be reduced bythe exclusion of certain additives such as water. When water is notpresent during the deposition of the first few hundred angstroms of theundercoat, the overall crystallite size is reduced. Haze can also bereduced by combining one or more of the above aspects. If TFA isincluded in the deposition process when water is being excluded, theoverall film haze is reduced. For example, when water is removed fromthe deposition of the first 50-60 nm of the TOSb layer, overall filmmorphology is reduced and haze values of ˜0.8% are achieved. If TFA isadded and water excluded from the deposition of the first 50-60 nm ofthe TOSb layer, similar morphology effects and haze values are recorded.

Fluorine, when added as a dopant into a tin oxide film, decreasesemissivity and increases film conductivity. However, it is notfunctioning as such a traditional dopant in this invention when it isadded to the antimony doped layer of the tin oxide coating. It functionsin the antimony doped layer as a modifier of the crystallite size of theantimony doped tin oxide as manifested in the reduction of overall filmhaze (measured on a hazemeter and confirmed by SEM micrographs). Theincrease in sheet resistance with the associated increase in emissivity,shown in the results in Table 3, confirms the function of the addedfluorine to the antimony doped tin oxide layer (TOSb). When fluorine ispresent in the TOSb layer, the resultant emissivity of the combinedlayer is increased, not decreased as would be expected if it werefunctioning as a dopant. While not willing to be bound to theexplanation, it is believed that fluorine may preferentially bind to theantimony sites thereby effectively removing both as dopants in the filmand hence the overall film emissivity would increase.

Another embodiment of the invention provides the ability to change thetransmitted color of the coated glass. Transmitted color refers to thecolor perceived by a viewer on the opposite side of the coated glassfrom the source of light being viewed, while reflected color is thecolor perceived by a viewer on the same side as the source of lightbeing viewed. Transmitted light can be effected by adding additionaldopiants to the NIR film. As previously explained, the NIR layercontains a dopant selected from the group consisting of antimony,tungsten, vanadium, iron, chromium, molybdenum, niobium, cobalt andnickel. The color of transmitted light through the NIR layer can bechanged by adding an additional dopant different then the first dopantin the NIR layer and selected from the group consisting of tungsten,vanadium, iron, chromium, molybdenum, niobium, cobalt, nickel or acombination of more then one additional dopant to the NIR layer. Thehaze additive, fluorine, can also effect transmitted color. As shown inexamples 40-43, the addition of a fluorine precursor, such astrifluoroacetic acid (TFA) to a NIR precursor solution such asSbCl₃/MBTC, produces a film whose transmitted color is gray versus ablue transmitted color for an antimony doped tin oxide layer withoutfluorine dopant. The additive has little or no effect on reflected lightand accordingly, a coated glass can be produced having a reflected lightthat is different then its transmitted light.

Dopants in the NIR layer such as vanadium, nickel, chromium andnon-traditional color additives such as trifluoroacetic acid (TFA) canbe added to the TO:Sb precursors in 1-5 wt % (based on the total wt ofprecursor and additive) to effect transmitted color changes in the finalfilm construction while not significantly affecting overall reflectedcolor neutrality.

The preferred embodiments of our invention will be exemplified by thefollowing examples. One skilled in the art will realize that minorvariations outside the embodiments stated herein do not depart from thespirit and scope of this invention.

The most preferred embodiments, at this time, to obtain a coated glasswith low e and NIR properties with neutral reflected color from a tinoxide coating composed of only two layers, irrespective of haze, aredescribed in Examples 1 to 30. One layer is about a 3000 Å thick TO:Ffilm (fluorine doped tin oxide) in combination with about a 2400 Å TO:Sb(antimony doped tin oxide) film on glass. The film thickness for theTO:F layer can range from ˜2800-3200 Å and still achieve the surprisingresult of a neutral reflected color. The fluorine concentration canrange from ˜1-5 atomic %. The TO:Sb film thickness can range from2200-2600 Å with an antimony concentration from 3-8% and still achievethe surprising result of a neutral reflected color for the coated glass.Within the preferred thickness and dopant concentration ranges of thepresent invention, a solar control coated glass can be produced having aNR layer and a low e layer and having a Neutral-blue Color for reflectedlight, i.e. coated glass having reflected light predominately withinC.I.E. chromaticity coordinates values of x between 0.285 and 0.310 andy between 0.295 and 0.325 as shown in FIG. 7 by a box labeledNeutral-blue Color.

All SHGC and U values in the tables have been determined using thesingle band approach of the NFRC Window 4.1 program. Use of the moreaccurate multiband approach (spectral data file required) will improvethe SHGC's by approximately 14%.

The C.I.E. tristimulus values for the reflected and transmitted colorsof the coated articles can be calculated according to ASTM Standard E308, with Illuminant C used as the standard illuminant. From this ASTMStandard E 308, the color of an object can be specified with one ofseveral different scales. The scale used for the coated articles in thisinvention is the C.I.E. 1931 chromaticity coordinates x and y. One caneasily translate to the C.I.E. 1976 L*, a*, b* opponent-color scale byusing the following equations:

x=X/(X+Y+Z)

y=(X+Y+Z)

L*=116(Y/Y _(n))^(⅓)−16

a*=500[(X/X _(n))^(⅓)−(Y/Y _(n))^(⅓)]

b*=200[(Y/Y _(n))^(⅓)−(Z/Z _(n))^(⅓)]

where X, Y, and Z are the C.I.E. tristimulus values of the coatedarticle, and X_(n), Y_(n), and Z_(n), are 98.074, 100.000, and 118.232,respectively, for Standard Illuminant C. from the L*, a*, b* values, thecolor saturation index, c*, can be calculated by the equationc*=[(a*)²+(b*)²]^(½). A color saturation index of 12 or less isconsidered neutral.

The definition of Neutral-blue Color for reflected light, i.e. coatedglass having reflected light predominately within C.I.E. chromaticitycoordinates values of x between 0.285 and 0.310 and y between 0.295 and0.325 as shown in FIG. 7 by a box labeled Neutral-blue Color correlateswith C.I.E. 1976 L*, a*, b* of 37.85, −1.25, −5.9 and 39.6, −2.25, 1.5.

A sample conversion follows:

Example 40 (Table 3) 5.5% SbCl₃ 300/240 (F/Sb/Glass) X = 9.797 Y = 9.404Z = 12.438 x = 0.310 y = 0.297 L* = 36.751 a* = 4.624 b* = −3.466 c* =5.778

Solar control properties of glass windows has been evaluated and ratedby the United States of America, Environmental Protection Agency usingan Energy Star rating system. An Energy Star rating for the CentralRegion of the United States requires a U-factor rating of 0.40 or lowerand a SHGC rating of 0.55 or below. An Energy Star rating for theSouthern Region of the United States requires a U-factor rating of 0.75or lower and a SHGC rating of 0.40 or below. Coated glass having the NIRand Low e coatings of the present invention and when incorporated intowindows of conventional design achieve the Energy Star ratings for theCentral and/or Southern Region. For example a Vertical slider designwindow 3 feet wide by 4 feet high and having a frame absorption value of0.5 as rated by the National Fenestration Rating Council (NFRC) andassembled with coated solar control glass of the present inventionhaving a NIR film and a low e film within the preferred ranges for aNeutral-Blue Color achieves a SHGC of less than 0.40 and a U value ofless than 0.64 for a monolith glass construction with a frame U-value of0.7 or less and achieves a SHGC of less than 0.38 and a U value of lessthan 0.48 for an Insulated Glass Unit (IGU) construction made up with2.5 mm clear lite, 0.5 inch air gap and NIR and Low e coatings on the #2surface of the outer lite and a frame U-value of 1.0 or less.

The examples will substantiate that with a minimum of two doped SnO₂layers, an excellent solar control coated glass can be produced having apreselected reflected color. Tables 1, 2 and 3 present the data whileFIGS. 5 and 6 show graphically how the solar properties of the coatedglass vary with dopant concentrations and film thickness primarily ofthe NIR film. FIG. 7 plots the x and y C.I.E. chromaticity coordinatesof a representative selection of coated glass of Examples 1 to 30. Asseen in FIG. 7, specific combinations of film thicknesses for both theNIR and low emissivity films; and specific dopant(s) concentrations canbe utilized to produce a coated, solar control glass with any desiredcolor for light reflected off the coated surface of the glass, such asred, green, yellow, blue and shades thereof or Neutral-blue Color. It isparticularly surprising that a Neutral-blue Color can be achieved with aNIR and a low emissivity layers but without an anti-iridescence layersuch as taught by Gordon.

While the inventive features of the present invention can be achievedwith only two layers, a NMR layer and a low emissivity layer, multilayerembodiments are within the scope and content of the invention. Themultilayers can be additional NIR and/or low emissivity layers or otherfunctional or decorative layers. Multilayer embodiments includeTOSb/TOF/TOSb/Glass, or TO/TOF/TOSb/Glass, or TO/TOSb/TOF/Glass with TObeing just a tin oxide film. When multiple NIR or low emissivity layersare used, the dopant concentrations or dopant selection in each NIR orlow emissivity film need not be the same. For example when two NIRlayers are used in combination with at least one low emissivity layer,one NIR layer can have a low level of antimony dopant (e.g. 2.5%) togive some reflectance in the mid IR range and one layer can have ahigher level (≧5%) to give NIR absorbency. The terms layer and film aregenerally used herein interchangeably except in the discussion ofgradient film depicted in FIG. 3 in which a portion of the film isreferred to as a layer having a dopant concentration different than thedopant concentration in another layer of the film. In the method ofmaking the coated glass of the present invention as demonstrated in theexamples, the glass is contacted sequentially with carrier gascontaining precursors. Accordingly, the glass may have a coating on itwhen it is contacted a second time with a carrier gas containingprecursors. Therefore, the term contacting glassy refers to eitherdirect contact or contact with one or more coatings previously depositedon the glass. The best ways to practice the haze reduction aspects ofthis invention are described in Examples 40-43 and 48-61. The resultsare summarized in Tables 3, 4, and 5.

EXAMPLES 1 TO 30

A 2.2 mm thick glass substrate (soda lime silica), two inches square,was heated on a hot block to 605 to 625° C. The substrate was positioned25 mm under the center section of a vertical concentric tube coatingnozzle. A carrier gas of dry air flowing at a rate of 15 liters perminute (l/min) was heated to 160° C. and passed through a hot wallvertical vaporizer. A liquid coating solution containing 95 wt %monobutyltin trichloride and ˜5 wt % antimony trichloride was fed to thevaporizer via a syringe pump at a volume flow designed to give a 0.5 mol% organotin concentration in the gas composition. A quantity of waterwas also fed into the vaporizer at a flow designed to give a 1.5 mol %water vapor in the gas mixture. The gas mixture was allowed to impingeon the glass substrate at a face velocity of 0.9 m/sec for ˜6.1 secondsresulting in the deposition of a film of antimony doped tin oxide ˜240nm thick. Immediately following, a second gas mixture was usedconsisting of a precursor composition of 95 wt % monobutyltintrichloride and 5 wt % trifluoroacetic acid, along with water in thesame concentrations and carrier gas as used before to deposit theantimony doped SnO₂ layer. This second gas mixture was allowed toimpinge on the coated substrate for ˜6.7 seconds. A film of ˜280 nm offluorine doped tin oxide was deposited. The bilayer film was very lightblue in transmission and reflection. The optical properties weremeasured on a UV/VIS/NIR spectrophotometer and the sheet resistance wasmeasured on a standard four point probe. The solar heat gaincoefficient, U value and visible transmission for the center of theglass were calculated using the Window 4.1 program developed by LawrenceBerkeley National Laboratory, Windows and Daylight Group, BuildingTechnologies Program, Energy and Environmental Division. The C.I.E.chromaticity x and y color coordinates were calculated using ASTME308-96 from the visible reflectance data between 380-770 nm and thetristimulus values for Illuminant C. The analysis results for this filmappears in Table 1, number 19. The procedure of this example wasrepeated 29 additional times with concentrations of chemical precursorsand deposition times varied in order to produce coated glass sampleshaving different thicknesses for the NIR and low emissivity layers anddifferent dopant concentrations. The results are presented in Table 1.

EXAMPLES 31 TO 38

The procedure of Example 1 was repeated, except that the vapor feedorder was reversed. The fluorine doped tin oxide film was depositedfirst for ˜8 seconds followed by the antimony doped tin oxide film for˜6 seconds. The resulting film was ˜540 nm thick and composed of a lowemissivity layer (TOF) of about 300 nm and a NIR layer (TOSb) of about240 nm and had a similar appearance and reflected light color(Neutral-blue Color) as the film in example 19. The analysis resultsappear in Table 2, number 31. The procedure of this example was repeated7 additional times with concentrations of chemical precursors anddeposition times varied in order to produce coated glass samples havingdifferent thicknesses for the NIR and low emissivity layers anddifferent dopant concentrations. The results are presented in Table 2.

EXAMPLE 39

The procedure of Example 1 was repeated but utilizing three precursorfeed mixtures. The composition of the third mixture was 90 wt %monobutyltin trichloride, 5 wt % trifluoroacetic acid, and 5 wt %antimony trichloride. A gradient film was deposited by first depositingonly the antimony doped tin oxide precursor of Example 1 for 70% of thetime needed to deposit 240 nm. Then the mixed antimony/fluorine dopedprecursor was started. Both precursor mixtures would continue for 20% ofthe total deposition time at which point the antimony precursor mixturewas turned off. The antimony/fluorine mixed precursor was continued forthe remaining 10% of the total deposition time for the 240 nm antimonyfilm. At this point, the fluorine doped tin oxide film precursor feedwas turned on. Both feeds were continued for 20% of the total timeneeded to deposit 300 nm of fluorine doped tin oxide. The mixedantimony/fluorine precursor feed was turned off and the fluorine dopedtin precursor was continued for the remaining deposition time for thefluorine dope film. The resultant gradient coating layer is light bluein transmitted and reflected color (x=0.292, y=0.316) a SHGC=0.50, a Uvalue=0.6, and a visible transmission about 45%. As shown in FIG. 3,surface 22 of gradient film 16 would have essentially 100% antimonydopant while surface 18 would have essentially 100% fluorine dopant witha gradient in dopant concentration between surfaces 18 and 22 and allwithin a film matrix of SnO₂.

EXAMPLES 40 TO 43

The procedure of Example 1 was used in Examples 40 to 43. The coatingcomposition for the NIR layer in Examples 41 and 43 was composed of afluorine, antimony, and tin precursor made by adding SbCl3 and TFA toMBTC. This precursor contained 0-5% by weight TFA, 5.2-5.5% by weightSbCl3, and the remainder MBTC, and was co-fed with water into the secondvaporizer. The carrier gas used for the second vaporizer was dry air ata rate of 15 l/min. The fluorine/antimony/tin precursor was added at arate of 0.5 mole percent of total carrier gas flow, the water was addedat a rate of 1.5 mole percent total carrier gas flow, and the vaporizertemperature was maintained at 160 C. A soda-lime-silica glass substratetwo inches square and 2.2 mm thick was preheated on a heater block to605 to 625 C. The heater block and substrate were then moved to aposition directly beneath the vertical coater nozzle, with the substratebeing 25 mm beneath the coater nozzle. F/Sb/Sn/H2O vapors from thesecond vaporizer were then directed onto the glass substrate, depositinga fluorine containing antimony doped tin oxide undercoat layer inexamples 41 and 43. The velocity of the carrier gas was 0.9 m/s and thethickness of the doped tin oxide film was ˜240 nm. Reaction byproductsand unreacted precursor vapors were exhausted from the substrate at arate of 18 l/min. After the antimony and fluorine doped tin oxideundercoat was deposited, the coater nozzle valve was switched from thesecond vaporizer feed to the first vaporizer feed. MBTC/TFA/H2O vaporsfrom the first vaporizer feed were then directed onto the substrate,depositing a layer of fluorine doped tin oxide directly on top of theantimony/fluorine tin oxide undercoat. The velocity of the carrier gaswas 0.9 m/s and the thickness of the fluorine doped tin oxide film was˜300 nm. The bilayer films in examples 41 and 43 (containing both F andSb in the NIR undercoat) were light grey in transmitted color andneutral in reflected color. Examples 40 and 42 essentially reproduceexamples 41 and 43 respectively but without fluorine in the NIRundercoat layer. The properties were measured and the results appear inTable 3. The results show how fluorine, as an additive in the NIR layer,acts as a color modifier as well as a haze reducer for both reflectedand transmitted color. The transmitted colors, T_(vis), x and y, of thefilms made with the TFA and Sb dopants in the NIR layer, Examples 41 and43, are more neutral in reflected color and greyer in transmitted colorthen those which only contained Sb as a dopant in the antimony doped tinoxide NIR layer in examples 40 and 42. Furthermore, the antimony dopedNIR layer with a color effecting quantity of fluorine dopant has greatertransmission of visible light (increase in T_(vis) from 54.5 to 58.5 inexample 41 versus example 42 with the some level of antimony dopant).

TABLE 3 Summary of Properties of Bilayer Films TOSb/TOF Ex. # 40 41 4243 Composit. F/Sb/G F/Sb-F/G F/Sb/G F/Sb-F/G % SbCl3 5.5 5.2 5.2 5.36 %Additive 0 TFA 5 TFA 0 TFA 2.5 TFA Thick. nm 300/240 300/240 300/240300/240 % Asol 45.5 35.7 41.8 39.1 % Tsol 45.0 54.2 48.2 50.6 % Rsol, 19.5 10.1 10.0 10.3 % Rsol, 2 8.0 8.9 8.4 8.7 % Tvis 50.9 58.5 54.5 55.6% Rvis, 1 9.4 10.1 10.4 10.3 % Rvis, 2 8.0 9.0 8.5 9.0 % Tuv 40.1 41.141.6 39.8 S. R. 11.9 13.7 11.8 12.5 Emis-cal 0.12 0.13 0.11 0.12 Glass L# 6235 6236 6237 6238 SHGCc 0.53 0.60 0.55 0.57 ″IG 0.45 0.52 0.47 0.49Uc 0.72 0.73 0.72 0.72 ″IG 0.27 0.28 0.27 0.27 Tvis-c 0.51 0.59 0.550.56 ″IG 0.46 0.53 0.50 0.51 R1 x 0.310 0.296 0.302 0.303 R1 y 0.2970.313 0.299 0.306 % Rvis 9.4 10.1 10.4 10.3 Tvis x 0.294 0.308 0.2970.304 Tvis y 0.308 0.315 0.310 0.314 % Haze 2.22 ± 0.18 1.60 ± 0.29 2.34± 0.19 1.72 ± 0.26

Examples 44 through 47 demonstrate the deposition of films with thefollowing composition: TOF/TOSb (low Sb conc.)/TOSb (high Sbconc.)/Glass, TOF/TOSb (high Sb conc.)/TOSb (low Sb conc.)/Glass, TOSb(low Sb)/TOF/TOSb (high Sb conc.)/Glass, and TOSb (high Sb)/TOF/TOSb(low Sb conc.)/Glass.

EXAMPLE 44

The procedure of Example 1 was repeated except that the glasstemperature was about 610° C. and the concentration of reagents wasabout 0.63 mol % in air flowing at a rate of 20 liters per minute. About400 Å of antimony doped tin oxide was deposited first from a liquidcoating solution composed of about 10 wt % antimony trichloride and ˜90%monobutyltin trichloride. Immediately following, a second layer of about2000 Å of antimony doped tin oxide from a liquid coating solutioncomposed of 3.25% antimony trichloride and 96.75% monobutlytintrichloride was deposited. A third layer composed of about 3000 Å offluorine doped tin oxide was deposited from a solution containing 5 wt %trifluoroacetic acid and 95 wt % monobutyltin trichloride. The resultingfilm appeared to have a light green-blue color for reflected light andlight blue color for transmitted light. The film properties weremeasured as described in Example 1. The visible light transmission was64% and the SHGC was calculated to be 0.56. The x and y coordinates forthe color of reflected light were 0.304 and 0.299, respectively, puttingthe film in the neutral-blue color quadrant of C.I.E. color space asdefined earlier.

EXAMPLE 45

The procedure of Example 44 was repeated, but this time the TOSb layerswere deposited in reverse order (sometimes referred to herein as reverseconstruction). The resulting film was blue-red in reflected color withcolor coordinates of (x) 0.330 and (y) 0.293, respectively. A visibletransmission of 59% and a SHGC of 0.54 were obtained. One skilled in theart will realize that the TOSb layers can be of different thicknessesand concentrations than described herein and still be within the scopeof this invention.

EXAMPLE 46

The procedure of Example 44 was repeated, but in this example thedeposition sequence of the fluorine doped tin oxide layer and the 3.25%antimony trichloride solution layer were reversed. The resulting filmhad a visible transmission of about 62%, a SHGC (if 0.55, and a neutralblue-red reflected color characterized by color coordinates (x) 0.311and (y) 0.311.

EXAMPLE 47

The procedure of Example 45 was repeated, but in this example thedeposition sequence of the fluorine doped tin oxide layer and the 10.0%antimony trichloride solution layer were reversed. The resulting filmhad a visible transmission of about 57%, a SHGC of 0.53, and a lightgreen reflected color characterized by color coordinates (x) 0.308 and(y) 0.341. One skilled in the art will realize that the TOSb layers canbe of different thicknesses and concentrations than described herein andstill be within the scope of this invention.

EXAMPLE 48

The procedure of Example 41 was repeated with the following changes. Theprecursor coating composition for the NIR layer was composed of 5% byweight TFA,4.35% by weight SbCl3, and the remainder MBTC. The carriergas used for the vaporization was dry air at a rate of 20l/min. Thefluorine/antimony/tin precursor was added at a rate of 1.5 mol percentof total carrier gas flow, the water was added at a rate of 7.5 molpercent total carrier gas flow, and the vaporizer temperature wasmaintained at 160 C. A soda-lime-silica glass substrate two inchessquare and 2.2 mm thick was preheated on a heater block to 640° C.Precursor vapors were directed onto the glass substrate at a velocity of˜1.2 m/s and a fluorine and antimony contraining tin oxide film of ˜240nm was deposited at a rate of ˜1200 Å/sec. Immediately after thisdeposition, a fluorine doped tin oxide layer of ˜300 nm was deposited atthe same rate from a vapor composition of 1.5 mol percent TFA/MBTC (5%by weight TFA and 95% by weight MBTC), 7.5 mol percent water vapor andthe remainder air. The bilayer film was blue-green in reflected colorand had a haze value of 1.20% as measured on a Gardner Hazemeter.

EXAMPLE 49

The procedure of Example 48 was repeated but water was omitted from thevapor stream for the deposition of the first ˜300-600 Å of the antimonyand fluorine containing tin oxide first layer. The resulting film had ameasured haze of 0.97%, a 20% reduction from the previous Example.

COMPARATIVE EXAMPLE 50

The procedure of Example 40 was repeated with the following changes. Theprecursor coating composition for the NIR layer was composed of 6.75% byweight SbCl3 and the remainder MBTC. The carrier gas used for thevaporization was dry air at a rate of 20 l/min. The antimony/tinprecursor was added at a rate of 1.5 mol percent of total (carrier gasflow, the water was added at a rate of 7.5 mol percent of total carriergas flow, and the vaporizer temperature was maintained at 160 C. Asoda-lime-silica glass substrate two inches square and 2.2 mm thick waspreheated on a heater block to 648° C. Precursor vapors were directedonto the glass substrate at a velocity of ˜1.2 m/s and an antimony dopedtin oxide film of ˜240 nm was deposited at a rate of ˜1200 Å/sec.Immediately after this deposition, a fluorine doped tin oxide layer of˜300 nm was deposited at the same rate from a vapor composition of 1.5mol percent TFA/MBTC (5% by weight TFA and 95% by weight MBTC), 7.5 molpercent water vapor and the remainder air. The bilayer film wasblue-green in reflected color and had a haze value of 1.34% as measuredon a Gardner Hazemeter.

EXAMPLE 51

The procedure of Example 50 was repeated but water was omitted from thevapor stream for the deposition of the first ˜300-600 Å of the antimonydoped tin oxide first layer. The resulting film had a measured haze of0.90%, a 33% reduction from the previous Example.

EXAMPLE 52

The procedure of Example 51 was repeated but 5% by weight TFA was addedto the precursor solution for the deposition of the first ˜300-600 Å ofthe antimony doped tin oxide first layer. The resulting film had ameasured haze of 0.83%, a 38% reduction from the haze in Example 50.

EXAMPLE 53

The procedure of Example 50 was repeated but 5% by weight TFA was addedto the precursor solution for the deposition of the antimony doped tinoxide first layer. The resulting bi layer film had a measured haze of1.17%.

EXAMPLE 54

The procedure of Example 40 was repeated with the following changes. Theprecursor coating composition for the NIR layer was composed of 6.75% byweight SbCl3 and the remainder MBTC. The carrier gas used for thevaporization was dry air at a rate of 20 l/min. The antimony/tinprecursor was added at a rate of 1.5 mol percent of total carrier gasflow, the water was added at a rate of 1.5 mol percent total carrier gasflow, and the vaporizer temperature was maintained at 160 C. Asoda-lime-silica glass substrate two inches square and 2.2 mm thick waspreheated on a heater block to 663° C. Precursor vapors were directedonto the glass substrate at a velocity of ˜1.2 m/s and an antimony dopedtin oxide film of ˜240 nm was deposited at a rate of ˜1050 Å/sec.Immediately after this deposition, a fluorine doped tin oxide layer of˜300 nm was deposited at the same rate from a vapor composition of 1.5mol percent TFA/MBTC (5% by weight TFA and 95% by weight MBTC), 1.5 molpercent water vapor and the remainder air. The bilayer film wasblue-green in reflected color and had a haze value of 1.13% as measuredon a Gardner Hazemeter.

EXAMPLE 55

The procedure of Example 54 was repeated but water was omitted from thevapor stream during the deposition of the first ˜300-600 Å of theantimony doped tin oxide first layer. The resulting film had a measuredhaze of 0.90%, a 20% reduction from the previous Example.

EXAMPLE 56

The procedure of Example 55 was repeated but 5% by weight TFA was addedto the precursor solution during the deposition of the first ˜300-600 Åof the antimony doped tin oxide first layer. The resulting film had ameasured haze of 0.70%, a 23% reduction from the previous Example.

EXAMPLE 57

The procedure of Example 54 was repeated but 5% by weight TFA was addedto the precursor solution used for the deposition of the antimony dopedtin oxide first layer. The resulting bilayer film had a measured haze of0.72%, a 36% reduction from the haze measured in Example 54.

The following examples illustrate the haze obtained when the bilayerfilm is deposited in reverse order.

EXAMPLE 58

The procedure of Example 31 was repeated with the following changes. Theprecursor coating, composition for the underlayer was composed of 5.0%by weight TFA and 95% by weight MBTC. The carrier gas used for thevaporization was dry air at a rate of 20 l/min. The precursor solutionwas added at a rate of 1.5 mol percent of total carrier gas flow, thewater was added at a rate of 1.5 mol percent of total carrier gas flow,and the vaporizer temperature was maintained at 160 C. Asoda-lime-silica glass substrate two inches square and 2.2 mm thick waspreheated on a heater block to 663° C. Precursor vapors were directedonto the glass substrate at a velocity of ˜1.2 m/s and a fluorine dopedtin oxide film of ˜300 nm was deposited at a rate of ˜1050 Å/sec.Immediately after this deposition, an antimony doped tin oxide layer of˜240 nm was deposited at the same rate from a vapor composition of 1.5mol percent SbCl₃/MBTC (6.75% by weight SbCl₃ and 93.25% by weightMBTC), 1.5 mol percent water vapor and the remainder air. The resultingbilayer film was neutral blue in reflected color and had a haze value of0.68% as measured on a Gardner Hazemeter.

EXAMPLE 59

The procedure of Example 58 was repeated, but 5% by weight TFA was addedto the precursor solution used for the deposition of the antimony dopedtin oxide first layer. The resulting bilayer film was a neutral blue inreflected color and had a haze value of 0.67%.

EXAMPLE 60

The procedure of Example 54 was repeated, but 2.9% by weight acetic acidwas added to a 5.75% by weight SbCl₃/MBTC precursor solution used forthe deposition of the antimony doped tin oxide first layer. Theresulting bilayer film was a neutral blue in reflected color and had ahaze value of 0.95%.

COMPARATIVE EXAMPLE 61

The procedure of Example 60 was repeated, but with no acetic acid in theprecursor solution. The resulting bilayer film was a neutral blue inreflected color and had a haze value of 1.37%.

The results of examples 48 to 61 are given in Tables 4 and 5

TABLE 4 Effects of TFA &/or H₂O On Haze of Bilayer Films Ex. # 48 49 5051 52 53 54 55 56 57 58 59 Composit.* 2 2 1 1 2 2 1 1 2 2 3 4 % SbCl34.35 4.35 6.75 6.75 6.75 6.75 6.75 6.75 6.75 6.75 6.75 6.75 % TFA 5 5 00 5 5 0 0 5 5 0 5 1^(st) 30-60 nm Y Y N N Y Y N N Y Y N Y In rest Y Y NN N Y N N N Y N Y H₂O/Sn 5 5 5 5 5 5 1 1 1 1 1 1 1^(st) 30-60 nm Y N Y NN Y Y N N Y Y Y In rest Y Y Y Y Y Y Y Y Y Y Y Y Rate (Å/s) ˜1200 ˜1200˜1200 ˜1200 ˜1200 ˜1200 ˜1050 ˜1050 ˜1050 ˜1050 ˜1050 ˜1050 Temp. ° C.640 640 648 648 648 648 663 663 663 663 663 663 % Haze 1.20 0.97 1.340.90 0.83 1.17 1.13 0.90 0.70 0.72 0.68 0.67 *Composition: 1 = 300 nmTOF/240 nm TOSb/G 2 = 300 nm TOF/240 nm TOSb F/G 3 = 240 nm TOSb/300 nmTOF/G 4 = 240 nm TOSb F/300 nm TOF/G

TABLE 5 Effects of Acetic Acid On Haze of Bilayer Films Ex. # 60 61Composit.* 2 2 % SbCl3 5.75 5.75 % HAc 2.9 0 1^(st) 30-60 nm Y N In restY N H₂O/Sn 1 1 1^(st) 30-60 nm Y Y In rest Y Y Rate (Å/s) ˜1050 ˜1050Temp. ° C. 663 663 % Haze 1.37 0.95 *Composition: 1 = 300 nm TOF/240 nmTOSb/G 2 = 300 nm TOF/240 nm TOSb.F/G 3 = 240 nm TOSb/300 nm TOF/G 4 =240 nm TOSb.F/300 nm TOF/G

Silica can also function as a haze reducing additive in the tin oxideNIR layer adjacent to the glass especially when added to the top portionof the NIR layer prior to the deposition of the low E layer on top ofthe NIR layer. The preferred silica precursor istetramethylcyclotetrasiloxane (TMCTS). A 33% haze reduction was obtainedwhen TMCTS was used in the last ˜600 Å of the undercoat. Examples 62 and63 and the results thereof in Table 6 illustrate the effects of silicaas a haze reducing additive in the antimony doped tin oxide layer.

EXAMPLE 62

The procedure of Example 1 was repeated with the following changes. Theprecursor coating composition for the NIR layer was composed of twosolutions, a 5.75% by weight SbCl3 with the remainder MBTC fed to bothvaporizers and a neat solution of tetramethylcyclotetrasiloxane (TMCTS)fed only to the second vaporizer. The carrier gas used for thevaporization was dry air at a rate of 15 l/min. The antimony/tinprecursor was added at a rate of 0.5 mol percent of total carrier gasflow, the water was added in the upstream mixing section of the coaterat a rate of 1.5 mol percent in total carrier gas flow, and thevaporizer temperature was maintained at 160° C. When the TMCTS was used,it was fed at a rate of 0.05 mol %. A soda-lime-silica glass substratetwo inches square and 2.2 mm thick was preheated on a heater block to663° C. NIR layer precursor vapors were directed onto the glasssubstrate at a velocity of ˜0.88 m/s and an antimony doped tin oxidefilm of ˜185 nm was deposited at a rate of ˜55 nm/sec. Immediately afterthis deposition, an antimony doped tin oxide film containing silica wasdeposited from the second vaporizer at the same rate to a thickness of˜61 nm. This was followed by a fluorine doped tin oxide layer of ˜298 nmwhich was deposited from the first vaporizer at the same rate from avapor composition of 0.5 mol percent TFA/MBTC (5% by weight TFA and 95%by weight MBTC), 1.5 mol percent water vapor and the remainder air. Thedeposited film was neutral blue in reflected color and had a haze valueof 0.81% as measured on a Gardner Hazemeter.

COMPARATIVE EXAMPLE 63

The procedure of Example 62 was repeated except that the antimony dopedtin oxide layer was 223 mn thick, no silica containing layer wasdeposited, and the TOF layer was 291 nm. The resulting film had a hazevalue of 1.20% as measured on the Gardner Hazemeter.

TABLE 6 Effect of TMCTS On Haze of Solar Control Films Ex. # 62 63TOF/TOSb- TOF/TOSb/ Composition Si/TOSb/G G % SbCl3 5.75 5.75 TOSb nm185 223 Mol TMCTS/mol Sn 0.1 0 TOSb-Si nm 61 0 TOF mn 298 291 Rate (Å/s)˜550 ˜550 Temp. ° C. 663 663 % Haze 0.81 1.20

We claim:
 1. A method of producing a tin oxide coated, solar controlglass having low haze of less than about 2.0% and having a NIR solarabsorbing layer and a low emissivity layer within said tin oxidecoating, comprising a glass substrate and a doped tin oxide coatinghaving at least two layers with one layer being a solar absorbing layercomprising SnO₂ containing a dopant selected from the group consistingof antimony, tungsten, vanadium, iron, chromium, molybdenum, niobium,cobalt, nickel and mixtures thereof and another layer being a lowemissivity layer comprising SnO₂ containing a dopant of fluorine orphosphorus and, wherein a portion of said solar absorbing layer containsfluorine in sufficient quantity to reduce the rugosity and haze for saidtin oxide coating and wherein the thickness of the NIR solar absorbinglayer is from 200 to 320 nanometers (nm) and the thickness of the lowemissivity layer is from 200 to 450 nm and the portion of said solarabsorbing layer containing fluorine to reduce the rugosity comprisesfrom 300 Angstroms (Å) to 600 Å of the thickness of the solar absorbinglayer and is located either adjacent to the interface between the solarabsorbing layer and the low emissivity layer, or is the portion of thesolar absorbing layer that is closest to the glass substrate, comprisingsequentially treating glass at a temperature above 400° C. with: a firstcarrier gas containing a source of oxygen, H₂O, a tin precursor and adopant precursor selected from the group consisting of antimonytrichloride, antimony pentachloride, antimony triacetate, antimonytriethoxide, antimony trifluoride, antimony pentafluoride, or antimonyacetylacetonate to form by pyrolysis a NIR layer comprising SnO₂containing an antimony dopant; an anhydrous second carrier comprisingoxygen, a tin precursor and a dopant precursor selected from the groupconsisting of antimony trichloride, antimony pentachloride, antimonytriacetate, antimony triethoxide, antimony trifluoride, antimonypentafluoride, or antimony acetylacetonate, and a haze reducing quantityof a haze reducing additive selected from the group consisting of aprecursor of fluorine, tetramethylcyclotetrasiloxane, HF, difluoroaceticacid, monofluoroacetic acid, antimony trifluoride, antimonypentafluoride, ethyl trifluoroacetoacetate, acetic, formic acid,propionic acid, methanesulfonic acid, butyric acid and its isomers,nitric acid or nitrous acid to form by pyrolysis a NIR layer comprisingSnO₂ containing an antimony dopant to form by pyrolysis a NIR layercomprising SnO₂ containing an antimony dopant and having reducedrugosity that contributes to reduced haze; a third carrier gascomprising gas containing a source of oxygen, H₂O, a tin precursor and adopant precursor selected from the group consisting of trifluoroaceticacid, ethyltrifluoroacetate, difluoroacetic acid, monofluoroacetic acid,ammonium fluoride, ammonium bifluoride, and hydrofluoric acid, to form alow emissivity layer comprising SnO₂ containing a fluorine dopant.
 2. Amethod of producing a tin oxide coated, solar control glass having lowhaze of less than about 2.0% and having a NIR solar absorbing layer anda low emissivity layer within said tin oxide coating, comprising a glasssubstrate and a doped tin oxide coating having at least two layers withone layer being a solar absorbing layer comprising SnO₂ containing adopant selected from the group consisting of antimony, tungsten,vanadium, iron, chromium, molybdenum, niobium, cobalt, nickel andmixtures thereof and another layer being a low emissivity layercomprising SnO₂ containing a dopant of fluorine or phosphorus and,wherein a portion of said solar absorbing layer contains fluorine insufficient quantity to reduce the rugosity and haze for said tin oxidecoating and wherein the thickness of the NIR solar absorbing layer isfrom 200 to 320 nanometers (nm) and the thickness of the low emissivitylayer is from 200 to 450 nm and the portion of said solar absorbinglayer containing fluorine to reduce the rugosity comprises from 300Angstroms (Å) to 600 Å of the thickness of the solar absorbing layer andis located either adjacent to the interface between the solar absorbinglayer and the low emissivity layer, or is the portion of the solarabsorbing layer that is closest to the glass substrate, comprisingsequentially treating glass at a temperature above 400° C. with: a firstcarrier gas containing a source of oxygen, H₂O, a tin precursor and adopant precursor selected from the group consisting of antimonytrichloride, antimony pentachloride, antimony triacetate, antimonytriethoxide, antimony trifluoride, antimony pentafluoride, or antimonyacetylacetonate to form by pyrolysis a NIR layer comprising SnO₂containing an antimony dopant; a second carrier comprising oxygen, tinprecursor, a dopant precursor selected from the group consisting ofantimony trichloride, antimony pentachloride, antimony triacetate,antimony triethoxide, antimony trifluoride, antimony pentafluoride, orantimony acetylacetonate, and a haze reducing quantity of a hazereducing additive selected from the group consisting of a precursor offluorine, tetramethylcyclotetrasiloxane, HF, difluoroacetic acid,monofluoroacetic acid, antimony trifluoride, antimony pentafluoride,ethyl trifluoroacetoacetate, acetic, formic acid, propionic acid,methanesulfonic acid, butyric acid and its isomers, nitric acid ornitrous acid to form by pyrolysis a NIR layer comprising SnO₂ containingan antimony dopant to form by pyrolysis a NIR layer comprising SnO₂containing an antimony dopant and having reduced rugosity thatcontributes to reduced haze; a third carrier gas comprising gascontaining a source of oxygen, H₂O, a tin precursor and a dopantprecursor selected from the group consisting of trifluoroacetic acid,ethyltrifluoroacetate, difluoroacetic acid, monofluoroacetic acid,ammonium fluoride, ammonium bifluoride, and hydrofluoric acid, to form alow emissivity layer comprising SnO₂ containing a fluorine dopant. 3.The method of claim 1 wherein said glass substrate is contacted with thesecond carrier gas before it is contacted with the first carrier gas. 4.The method of claim 1 wherein said glass substrate is contacted with thesecond carrier gas before it is contacted with the first carrier gas. 5.The method of claim 2 wherein said glass substrate is contacted with thesecond carrier gas before it is contacted with the first carrier gas andthe haze reducing additive is a selection other thantetramethylcyclotetrasiloxane.
 6. The method of claim 2 wherein saidglass substrate is contacted with the first carrier gas before it iscontacted with the second carrier gas and the haze reducing additive istetramethylcyclotetrasiloxane.
 7. The method of claim 5 wherein saidsecond carrier gas is anhydrous.